1. Field of the Invention
The invention in general relates to transmission of TV signals, and particularly to the transmission of such signals over long electromechanical cables.
2. Description of the Prior Art
In one type of underwater survey system, an underwater carrier vehicle is towed over the sea bottom by means of a long electromechanical cable connected to a surface towing vessel. The carrier vehicle includes a variety of sensor systems each of which must transmit their respective signals up the cable to a receiving location from which command and control signals are transmitted down the cable to the various systems.
For various mechanical reasons, some systems require a tow cable of several ten thousands of feet, whose frequency response is considerably worse than other cables not requiring the stringent mechanical performance. With the mechanically preferred cable, transmission of TV signals directly up the cable is impossible due to the severe attentuation of the long cable and to the fact that the frequency spectrum for the TV signals is limited due to the frequency band reserved for the other sensor systems. In addition, during the checkout phase of the equipment prior to carrier development, where the carrier is located close to or on the towing vessel there is an unavoidable signal leak-through problem which tends to increase with frequency, and which causes a severe degradation of the TV picture displayed on the monitor at the receiver location. This problem is even more severe during initial checkout at the factory where the electrical components are powered from a common 110 volt distribution source.